1. Field of the Invention
The present invention relates to a data multiplex broadcasting system in which a plural kinds of data are multiplexed to be transmitted, and, in particular, to a data multiplex broadcasting system suitable for recognizing a start of broadcasting of a particular content on the receiving side.
2. Description of Related Art
In RDS (Radio Data System) and DAB (Digital Audio Broadcasting), programme-associated information or independent information is multiplexed into audio information to be broadcasted. In RDS and DAB, audio information is sent being multiplexed with information called M/S (Music/Speech) flag which indicates whether the content of the audio information in question belongs to the category of music or the category of speech. On the receiving side, by referring to this flag, it is easy to recognize a point of time at which a broadcast of a piece of music starts after speech of a speaker in a broadcast programme, for example. In other words, by referring to this M/S flag, it is easy to record a piece of music broadcasted during a broadcast programme, onto an audio recording device such as an MD (Mini Disk) recorder from the beginning of the music piece in question.
In the case of RDS, when a programme is broadcasted, information associated to the contents of the programme is subjected to multiplex modulation as RDS signal, and various services can be supplied to radio listeners based on the RDS signal demodulated on the receiving side.
This RDS signal is obtained by using a subcarrier of 57 kHz outside the frequency band of the FM-modulated wave, and by subjecting this subcarrier to amplitude modulation with coded information data signal associated to programme contents. This amplitude-modulated subcarrier is subjected to frequency modulation onto a main carrier and then broadcasted.
In FIG. 14, RDS signal is repeatedly multiplexed and transmitted by groups each of which consists of 104 bits. Each group consists of 4 blocks, and each block includes 26 bits. More particularly, the block consists of 16 bits of an information word and 10 bits of a check word.
Further, each group is classified into 16 types, Type 0 through Type 15, depending on its contents. In addition, for each type of group, one of two versions, A and B, is defined.
For example, 0A group is defined as basic tuning and switching information, and includes a programme identification code (PI code), a traffic-information-programme identification code (TP code), programme station code (PS code), and the like.
Information indicating whether contents of a broadcast belong to the category of music or the category of speech is included in a second block of 0A group, 0B group and 15B group, and a fourth block of 15B group. This information is called M/S (Music/Speech) flag, as described above. When the value of M/S flag is 0, it shows that the current broadcast contents belong to the category of xe2x80x9cspeechxe2x80x9d, and, when its value is 1, it shows the current broadcast contents belong to the category of xe2x80x9cmusicxe2x80x9d. M/S flag is assigned, for example, to 13th bit 521 of the second block in FIG. 14.
On the receiving side, by receiving and demodulating this RDS signal, and by extracting M/S flag included in the 0A group, 0B group or 15B group, it is possible to recognize whether the current broadcast contents belong to the category of speech or to the category of music. Accordingly, by continuously monitoring this M/S flag, it is possible to recognize a point of time at which a broadcast of a piece of music starts after speech of a speaker in a broadcast programme, for example. Accordingly, it is possible to record apiece of music by an audio recording device such as an MD player, from the beginning of the music.
On the other hand, in the case of DAB, it is also possible to multiplex and transmit information similar to that in RDS. DAB is digital audio broadcasting in which Orthogonal Frequency Division Multiplex system (OFDM system) is employed to carry out multiplex modulation, and audio information is encoded in accordance with MPEG Layer II (International Standard system ISO/IEC 11172-3 Layer II).
In FIG. 15, an audio frame of DAB has a frame length of 24 ms, and is slightly different from a frame of MPEG. PAD (Programme Associated Data) included in this audio frame is for transmitting information associated with the programme. Utilizing this PAD, it is possible to transmit information such as a programme name, a record number, dynamic range control information, and the like. Further, PAD includes M/S (Music/Speech) flag that indicates whether broadcast contents belong to the category of music or the category of speech.
Accordingly, in the case of DAB, by extracting PAD included in an audio frame and referring to the content of M/S flag included in PAD, on the receiving side, it is also possible to recognize a point of time at which a broadcast of a piece of music starts after speech of a speaker, for example, similarly to RDS. Thus, it is possible to record a piece of music from the beginning by an audio recording device such as an MD player.
As described above, M/S flag indicates whether broadcast contents on the air belong to the category of music or the category of speech. In other words, it is a flag showing a category of broadcast contents on the air. However, use of M/S flag causes following problems in record control in an audio recording device such as an MD player.
Namely, when a plurality of music pieces are successively broadcasted, and it is desired to record a particular music piece out of these music pieces, the record control using M/S flag is not applicable to that situation. Accordingly, an operator must start a recording operation on the audio recording device in a timing synchronized a point of time at which that particular piece of music is actually started to be broadcasted. On that occasion, if the recording operation deviates from the actual point of time when the broadcast of the music piece is started to be transmitted, it is probable that failure such as so-called xe2x80x9cheadlessxe2x80x9d may be caused.
Further, as described above, even if plural pieces of music are to be successively broadcasted immediately after speech in a broadcast, it is possible to utilize M/S flag for automatic start of recording in synchronization with start of broadcasting the first piece of music. However, it is impossible to automatically stop recording operation in synchronization with a start of broadcast of a music piece next to the first-broadcasted one. In other words, it is impossible to record only the first music piece. Accordingly, an operator must stop recording of the audio recording device in synchronization with an actual end of broadcasting of the music piece which is being recorded.
The present invention has been made taking the above situation into consideration. An object of the present invention is to make it possible to easily recognize divisional point of respective content elements on the receiving side, even when the content elements of the same category are successively broadcasted. In detail, an object of the present invention is to provide a data multiplex broadcasting method, a switcher, a data multiplex transmitting device, a receiving device, a system controller, and a recording device which are able to support easy recognition of divisional point of respective content elements on the receiving side when the content elements of the same category are successively broadcasted.
To attain the above object, in the data multiplex broadcasting method of the present invention, information which can specify a start or end of each content element is multiplexed to data expressing broadcast contents and broadcasted when each content element of the broadcast contents belongs to the same category.
In detail, in the case that broadcast data expressing broadcast contents is formed of a plurality of successive element data, each of which expresses a content element belonging to the same category, a code whose state changes in synchronism with a start and/or end of each element data which is a constituent of said broadcast data is multiplexed to said broadcast data to be broadcasted.
Or, in the case that broadcast data expressing broadcast contents is formed of a plurality of successive element data, each of which expresses a content element belonging to the same category, a code expressing the number of element data which have been already transmitted or have not been transmitted yet among the element data which constitute the broadcast data is multiplexed to said broadcast data, in synchronism with a start or end of each of the element data constituting the broadcast data.
Or, a code, whose state changes in synchronism with switching of input sources of broadcast data expressing broadcast contents, is multiplexed to said broadcast data to be broadcasted.
Further, to attain the above objects, a switcher of the present invention generates information that can specify switching of input lines, i.e., switching of the content elements, in the case that the input lines are switched thereby to include a plurality of content elements into broadcast data expressing broadcast contents.
In detail, the switcher comprises: an input interface means for receiving element data through a plurality of lines; a line selection means for selecting element data of some one line out of the element data received by said input interface means through a plurality of lines and for generating a code when the selected line is changed, said code changing its state in synchronism with said change of the selected line; and an output interface means for transmitting the element data selected by and the code generated by said line selection means.
Further, to attain the above objects, a source controller of the present invention generates information that can specify switching of the information output devices, i.e., switching of the content elements, when a plurality of information output devices are controlled in their starts of output thereby to include a plurality of content elements into broadcast data expressing broadcast contents.
In detail, the source controller comprises: a control means for controlling a plurality of information output devices, at least concerning their starting of output; a switching means for selecting some one out of said plurality of information output devices; and a signal generating means for outputting a signal whose state changes in synchronism with a point of time at which said switching means switches the information output device to be selected.
Or, the source controller comprises: a control means for controlling a plurality of information output devices, at least concerning their starting of output; a switching means for selecting some one out of said plurality of information output devices; and a signal generating means for deciding a content of associated information associated to information of a content element outputted by the information output device after switched, said associated information including a code whose state changes in synchronism with a point of time of switching the information output device to be selected, and for generating a signal indicating said decided content.
Further, to attain the above objects, a data multiplex system of the present invention generates information that can specify switching of the information output device performing output, i.e., switching of content elements, and multiplexes said information into the broadcast data to broadcast the multiplexed data, when a plurality of information output devices are controlled concerning their respective starting of output thereby to include a plurality of content elements into broadcast data expressing broadcast contents.
In detail, the data multiplex system comprises: a plurality of information output devices; the above-described source controller; a programme configuration information generating means for generating programme configuration information in accordance with the content indicated by the signal supplied from the source controller; an encoding means for receiving information of the content element outputted by the information output device selected by the source controller and for encoding the received information; a multiplexing means for multiplexing the information of the content element encoded by the encoding means and the programme configuration information generated by the programme configuration information generating means, and for generating a multiplex signal; a modulating means for modulating the multiplex signal generated by the multiplexing means; and a transmitting means for broadcasting the multiplex signal modulated by the modulating means.
Further, to attain the above objects, the receiving device of the present invention monitors information that can specify switching of respective content elements included in the broadcast data and that is multiplexed to the multiplex signal broadcasted by the data multiplex system, so as to detect points at which respective content elements are switched.
In detail, the receiving device comprises: an extracting means for extracting a music piece broadcast end bit and an M/S flag multiplexed into the broadcast data, as the information that can specify switching of respective content elements included in the broadcast data, said music piece broadcast end bit being reversed in its logic in synchronism with an end of the music piece broadcasted, and the M/S flag indicating music or speech; and an outputting means for outputting a signal indicating a divisional point between music pieces in synchronism with a point of time at which the music piece broadcast end bit is reversed in its logic, in a state that the M/S flag indicates music.
Or, the receiving device comprises: an extracting means for extracting an information bit indicating a number of remaining music pieces to be broadcasted and an M/S flag indicating music or speech, the information bit and M/S flag being multiplexed into broadcast data, as information that can specify switching of respective content elements included in the broadcast data; and a signal generating means for generating a signal that indicates a value indicated by the information bit when the M/S flag indicates music.
Further, to attain the above-described objects, the system controller of the present invention utilizes the points of switching content elements (music pieces) detected by said receiving device, so as to make a recording device to record a desired content element.
In detail, the system controller comprises: an interface for receiving operator""s designation of an ordinal number corresponding to a music piece to be recorded; and a control part for causing the recording device to start to record when the receiving device detects a point of starting broadcast of the music piece corresponding to said designated ordinal number.
Further, to attain the above-described objects, the recording device of the present invention can record only desired content elements by monitoring the information that can specify switching of respective content elements included in the broadcast data and is multiplexed in the multiplex signal transmitted by the above-described data multiplex system, so as to detect the points of switching respective content elements.
In detail, the recording device comprises: a recording means for recording broadcast data; an interface means for receiving an instruction to start recording; an extracting means for extracting broadcast data expressing broadcast contents and a divisional point signal for contents element data expressing respective content elements constituting the broadcast data, from the multiplex signal received; a buffer memory means for storing said extracted broadcast data and divisional point signal over a certain period; a detecting means for detecting a point at which a state of the divisional point signal stored in the buffer memory means changes; and a transfer means for supplying the broadcast data stored in the buffer memory means when and after the state of the detected divisional point signal changed, when the instruction is received by the interface means.